Embodiments of the present invention are related to malleable, primarily metallic, gaskets for sealing joints between portions of a fluid pathway. Many combinations of interface structures and associated gaskets are well known in the design of fluid delivery apparatus. These structures include flanges, glands, component connections, and other functions that enable mechanical assembly of various apparatus elements forming a collection of interconnected fluid pathways. Representative fluid delivery apparatus are found among industrial equipment producing fine chemicals, petroleum products, flat panel electronic displays, or semiconductors, and may be subjected to vacuum, or pressure, or purity requirements, and combinations thereof. Fluid pathways among elements intended for manipulating process materials within semiconductor manufacturing equipment usually require attention to maintaining high purity of the delivered reactants and also typically have a much smaller cross-section than fluid pathways used in petrochemical plants, for example. In many cases practitioners have found metallic gaskets provide superior performance, particularly regarding diffusion of process fluid or contaminants through the gasket and consequent resistance to undesirable leakage, in preference over polymer materials.
One known type of fluid pathway joint uses a ring-shaped gasket, initially flat in a radial direction, axially compressed between nominally identical shaped annular projections that surround circular conduit openings of opposing apparatus elements. The annular projections are urged axially toward each other causing permanent plastic deformation of the ductile metallic gasket creating a seal that will resist leakage of even difficult to contain fluids such as helium. Representative examples of such joints may be seen in U.S. Pat. No. 3,208,758 issued to Carlson and Wheeler (familiarly known as the Varian® Conflat® flange), in U.S. Pat. No. 3,521,910 issued to Callahan and Wennerstrom (familiarly known as the Swagelok® VCR® fitting), and in U.S. Pat. No. 4,303,251 issued to Harra and Nystrom.
Another known type of fluid pathway joint uses a ring-shaped gasket of predetermined cross sectional profile compressed between nominally identical shaped annular projections that surround circular conduit openings of opposing apparatus elements. Representative examples of such joints may be seen in U.S. Pat. No. 4,854,597 issued to Leigh, in U.S. Pat. No. 5,505,464 issued to McGarvey, and in U.S. Pat. No. 6,135,155 issued to Ohmi et al. (an early version of the W-Seal joint type). The patent to Ohmi et al. additionally provides a separate retainer means for holding and centering the gasket during joint assembly. Other separate retainer structures may also be seen in U.S. Pat. No. 5,673,946 and U.S. Pat. No. 5,758,910 both issued to Barber and Aldridge, and in U.S. Pat. No. 7,140,647 issued to Ohmi et al.
Yet another known type of fluid pathway joint (familiarly known as the C-Seal joint type) uses a ring-shaped metallic gasket of complex shape compressed between opposing apparatus elements having simple flat surfaces in contact with the gasket. Most usually the face of at least one apparatus element has a circular counterbore depression to receive the gasket. Representative examples of such joints may be seen in U.S. Pat. No. 5,797,604 issued to Inagaki et al., in U.S. Pat. No. 6,357,760 and U.S. Pat. No. 6,688,608 both issued to Doyle, and in U.S. Pat. No. 6,409,180 issued to Spence & Felber. The '180 patent issued to Spence and Felber additionally provides a separate retainer means for holding and centering the gasket during joint assembly. Other separate retainer structures may also be seen in U.S. Pat. No. 5,984,318 issued to Kojima and Aoyama, in U.S. Pat. No. 6,845,984 issued to Doyle, and in U.S. Pat. No. 6,945,539 issued to Whitlow et al. Additionally, U.S. Pat. No. 5,992,463 issued to the present inventor Kim Ngoc Vu et al, and U.S. Pat. No. 5,730,448 issued to Swensen et al., show a suitably thick retainer may instead provide the compression limiting function of a counterbore sidewall and allow use of a gasket between simple flat opposing faces.
High purity fluid delivery components and fluid pathway elements are often made from a vacuum refined variation of type 316L stainless steel or nickel alloys such as Hastelloy® C-22®. Both of those metallic materials can only be hardened by mechanical work rather than heat treatments and consequently are at risk of being damaged by the localized forces accompanying metallic gaskets. High purity fluid delivery components made from polymer materials are also well known and often used when controlling flow of certain liquid fluids where potential contamination with metallic ions is a concern. In many polymer apparatus designs, fluid pathway joints also use opposed flat surfaces (with or without counterbores) with an interposed gasket. Gaskets made from polymer materials for use in such joints may also benefit from the inventive designs described in this disclosure.